It is known that significant quantities of lubricants, cutting oils, and cutting fluids are used in industrial machining operations. In the automotive industry and related operations, these "oils", when spent, are sent to the plant's waste treatment facility where they are typically combined with other plant waste streams. In simple form, these "oils" are undiluted petroleum oils and an emulsifier. However, in practice, they typically contain fatty acids, surfactants, biocides, antioxidants and many other additives. Also, they may be contaminated with synthetic oils. These industrial wastes typically contain from 0.05% to 4% oil content by volume.
In view of recent rigid environmental standards, increases in oil prices and decreases in oil supply, it has become very important to recover these oils for reuse. Since the oily wastes are typically emulsions of oil in water, recovery can be accomplished using the well-known "demulsification - flocculation" separating process. For example, it has been known to incorporate a combination acid-alum treatment into an oil recovery process. At low pH (2 to 3), the aluminum complex exhibits a state of high positive valence. A nearly neutral-charged insoluble aluminum hydroxide is formed by hydrolyzation of alum at pH 6 to 7. Further pH increases produce the negatively-charged aluminate and solubility increases. The positively-charged alum at low pH neutralizes the negative stabilizing charge on the oil droplets of the emulsion to cause demulsification and coagulation. Upon hydrolysis the alum provides a surface for oil adsorption by van der Waals forces to cause flocculation. Accordingly, the pH of the oily waste is kept low to promote oil demulsification. In some applications, the oil is then floated and recovered by skimming. The pH is then elevated to cause aluminum hydroxide to precipitate, resulting in a floc which adsorbs the remaining oil. Alternatively, the flocculation recovery step could be used as a one-step method to recover the oil. However, these acid-alum treatment processes have inherent drawbacks. For example, large quantities of acid are necessary to lower the oily waste pH. Also, special equipment is necessary for handling such a low pH and special metallurgy is needed to prevent corrosion. In addition, neutralizing the low pH water increases operating costs. Also, high alum feed-rates cause large sludge volumes, thus complicating oil recovery and creating a disposal problem. Finally, oil is extremely hard to extract from alum floc.
Accordingly, it is an object of the present invention to provide a novel water-soluble cationic polymeric material useable in separating oil from industrial oily wastes, which material would overcome the above-noted drawbacks of the acid-alum process. In this regard, the present inventors discovered that the separation of oil from oil-containing wastes could be effectively achieved by utilizing a water-soluble cationic polymer obtained by the polymerization of an epihalohydrin with a specific family of alkylene polyamine.